Copper alloys are used worldwide in applications with special requirements such as corrosion, oxidation, cavitation or wear resistance. The aluminum-bronze family, usually containing iron and, sometimes, nickel, is a very versatile member of the copper alloy system.
Aluminum-bronze is produced by both cast and wrought methods. Its tensile properties can be varied from a low of 50 ksi (345M Pa) to as high as 130 ksi (896M Pa). Hardness values range from 77 Rockewell F and 40 Rockwell C. Resistance to wear is excellent, especially when subjected to heavy unit loads. Like many other copper alloys, it has excellent corrosion resistance to many media.
All of the aluminum-bronze alloys are weldable, both for joining and overlay or surfacing. They are useful not only for welding to other copper aluminum alloys but also when many other copper alloys and even dissimilar metals are involved.
Weldments involving joining include such diverse applications as pump discharge columns, mixing bowls and paddles for dynamite and other explosives, submarine auxiliary propulsion units, large diameter pipe, chemical reaction vessels, etc.
Overlaying or surfacing, preferably with strip electrodes, on the other hand, is used for both initial installation and repair of such items as forming dies, hydroelectric wicket gates, turbine wear rings, marine propeller blades, torpedo ejection systems, ordnance such as gunslides and rotating bands and for many other applications.
To date, the welding methods most successfully employed with aluminum-bronze alloys have been the shielded metal-arc and gas metal-arc methods. However, when considering the high cost of labor it is recognized that welding by use of shielded metal-arc or gas metal-arc methods results in a relatively slow and expensive process.
If a more cost-effective method of welding could be developed, the usage of aluminum-bronze would be greatly enhanced. For example, if the surfacing or overlaying of aluminum-bronze were less expensive it could be used to provide protection for off-shore platform legs and riser pipes in the wave, tidal and splash zone, spiral wound and welded pipe, internal surfaces of pressure vessels in the chemical and petro-chemical industries, discs for large butterfly valves, and the like.
A proven cost-effective method for welding and overlaying steel, stainless steel, Monel and other competitive materials is known as submerged-arc welding. Submerged arc welding is a process wherein a blanket of granular flux is used to shield a welding electrode and the molten base metal of the parts being welded from the atmosphere.
The ideal flux for submerged arc welding also cleans the molten metal pool; it favorably modifies the chemical composition of the weld metal; and, it favorably influences the shape of the weld bead and its mechanical properties. It also forms a readily removable or free peeling fused slag to facilitate cleaning after use.
The submerged arc welding process is widely used because of its many advantages. It is readily adapted to the use of automatic equipment; the process allows for high deposition of weld metal; the process can be carried out at speeds significantly higher than those of other known welding techniques; and, it provides welds or overlays of larger thickness than other methods.
Unfortunately, it has not been possible to use the submerged arc welding process with copper alloys, such as aluminum-bronze because of the lack of suitable welding fluxes.